The present invention relates to a laminate sheet and a card capable of imparting an improved bending-resisting property and image durability to a thermally transferred image.
In the conventional technology, various printed letters or the like and images have been widely formed by thermal transfer methods.
These thermal transfer methods are approximately classified into two types, one being a so-called wax-type (heat-fusion type) in which a thermal transfer layer is softened by heating and thermally transferred to a material on which an image is being transferred and the other being a so-called sublimation type in which a dye in a thermal transferred layer is sublimated (heat transfer) and only the dye is thermally transferred to a material on which an image is being transferred.
In both types, a print image to be formed is merely caused to adhere or dyed on the surface of a thermal transfer image sheet, so that the image durability such as anti-friction property and an anti-solvent property of the print image is inferior, and when the image sheet contacts another article, colors of the transfer sheet may be transferred, thus damaging the surface of the article.
In order to solve such problems, the prior art further provides a transfer method in which a transparent sheet provided with a bonding layer is preliminarily laminated on the image surface of the print image to be thermally transferred, for example, as disclosed in Japanese Patent Laid-Open Specification No. 1-237193.
However, in the case where such laminate sheet of conventional art is applied to cards such as identification cards and the like which are required to be prevented from being counterfeited or falsified by forcibly peeling of the laminate sheet, there is a possibility of the laminate sheet being peeled off without damaging the transferred image on the card, and it becomes possible to falsify or deform the card. Accordingly, in order to obviate such possibility, it is necessary to strongly bond the laminate sheet to the card to the extent that the transferred image will be damaged if the laminate sheet is forcibly peeled off.
Furthermore, since such cards are usually subjected to severe and repeated handling, it is also necessary for such cards to have improved flexibility and bending-resisting property. However, in the conventional laminate sheet card, there is a possibility of the bonded layer being locally peeled off with repeated use in a bent manner, and an opaque portion may be formed in the card, resulting in the degradation of image on the card. These problems are conspicuous in pouch-cards in which the laminate sheet covers the peripheral portion of the card as well as both sides of the image, and an overlap width portion is also bonded thereby to entirely wrap the image and a flash-cut type card in which the overlap width portion of the pouch-card is cut.
Still further, in the case where an image to be protected on the card is of a sublimation transfer type image, it is necessary to prevent bleeding of the dye image due to the formation of the bonding layer.